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Bats & Wind Energy

Dead hoary bat next to a turbine Photo Courtesy of Michael Schirmacher

The conservation calculus for wind energy changed dramatically in the fall of 2003. Up until that point, bird fatalities had been the primary environmental concern at wind turbines, particularly raptors. Then a study in West Virginia estimated 1,400 to 4,000 bat fatalities during late-summer and autumn, and the concerns about environmental impacts of wind power began to change across North America.

What causes bat fatalities?

Current research suggests that the overwhelming majority of bat fatalities are caused by collisions with turbine blades. There is some evidence to suggest that a phenomenon known as barotrauma may result in a small proportion of bat deaths, as well. Barotrauma involves tissue damage to air-containing structures, such as lungs, caused by rapid or excessive pressure change. Air pressure changes can occur at the edges of moving turbine blades and may help explain some bat fatalities.

Fatalities

Between 2000 and 2011, an estimated 650,000 to 1.3 million bats have died from collisions with wind turbines in the United States and Canada (Arnett and Baerwald 2013). Additionally, as many as 400,000 estimated fatalities may have occurred in 2012.

With wind-generated energy expected to expand from the current 82,000 MW to 224,000 MW by 2030 (U.S.DOE Wind Vision 2015), the impact on bat populations from this build-out could be devastating unless solutions to minimize fatalities are developed and implemented.

In the U.S. and Canada, at least 24 species of bats have been reported as killed by wind turbines. The hoary bat (Lasiurus cinereus), eastern red bat (Lasiurus borealis) and silver-haired bat (Lasionycteris noctivagans), all migratory tree bats, account for nearly 78% of the kills north of Mexico. The hoary bat accounts for 38% of the fatalities. A new study that looked at hoary bat mortality at wind energy facilities during 2014 revealed that populations of the species may plunge by a staggering 90 percent in the next 50 years if no action is taken.

At some sites in the Midwest and Eastern U.S., species that are already battered by White-nose Syndrome (WNS), can account for up to 60% of wind-energy fatalities.

Two federally endangered species, the Hawaiian hoary bat (Lasiurus cinereus semotus) and the Indiana myotis (Myotis sodalis), also have been killed by turbines.